"I wasn't diagnosed with PCOS until I was 22, but I had been used to the stares for years. For a while I worked in a mobile phone shop and often, when I refused a customer a contract – usually a young man – he would get cross and make a mean comment about my moustache. It was very hurtful," she said in a phone interview this week.

Last month O'Neill, an account manager for a kitchen and bathroom company, successfully completed another charity feat by not touching alcohol for the Go Sober October campaign for Macmillan Cancer Support. "I realised I must have some willpower and I remembered that my cousin had done Movember a few times before, so I decided to do it too. I think I've stolen his thunder a little now."

At the start of November, O'Neill had her first ever shave, which she filmed for posterity – "I've never done that before – usually I use some special cream I get prescribed by my GP, or tweezers or an epilator," she said. "But for once I want to grow the best moustache I can, so I thought I'd shave in case that encouraged hair regrowth." O'Neill's facial hair is mostly blonde, with the occasional ginger sprouting. Seen from the wrong angle, she says, it can sometimes "look as though I've got a handlebar moustache."

When I spoke to O'Neill, she was on day six and rather enjoying the experience. "It's very liberating not having to spend half an hour sorting my moustache out," she said. "At the moment it's very bristly. When I kissed my partner goodbye this morning, she complained that I'd stabbed her. Some dark hairs have started sprouting from my chin too, like a mini goatee."

O'Neill says her girlfriend, Tina, is "really proud" of what she is doing. But she hasn't decided yet whether to make her moustache a permanent feature. "At the minute, it's temporary," she said. "But who knows how I'll feel at the end of the month?"